Water filter type
Water softeners
An ion exchange system that swaps calcium and magnesium for sodium or potassium, which is the only method that actually removes hardness minerals from the water.
How ion exchange works, in plain terms
A softener is a tank of resin beads carrying sodium ions. Hard water flows through, the calcium and magnesium stick to the resin, and sodium releases into the water in their place. That exchange is why softened water has a slightly higher sodium content and why the minerals genuinely leave the water rather than being altered in place.
Once the resin is saturated it cannot hold any more hardness, so the unit regenerates. It draws brine from the salt tank, flushes the calcium and magnesium off the resin, and sends that waste to a drain. Then the cycle starts again.
This is the only common residential method that removes hardness. Anything sold as a softener that requires no salt and no drain is doing something else, and that distinction is covered on our salt-free conditioners page.
Sizing by grains, not by house
A softener is sized on grain capacity: your hardness in grains per gallon, multiplied by the gallons your household uses between regenerations. Get this wrong in either direction and it costs you.
Undersized units regenerate too often, which wastes salt and water and wears the control valve. Oversized units sit with water in the resin bed for long periods between cycles, which is its own problem.
This is why we measure hardness before quoting rather than after. A figure from the utility report is a useful starting point, but it is a system average and your tap can differ from it.
The honest arguments against softening
Softened water contains added sodium. For most people the amount is small relative to diet, but if you are on a restricted sodium intake it is worth discussing with a clinician. Potassium chloride is an alternative, and it costs more to run.
Some people dislike how softened water feels, describing it as slippery, because soap rinses differently without hardness minerals to react with. That is not a fault and it does not go away.
Some municipalities restrict brine discharge to the sanitary sewer. Where that applies, a softener may not be permitted at all, and we check before quoting rather than after installing.
If your hardness is mild and nothing is scaling, the honest recommendation is to leave it alone.
What it reduces, and under which standard
Each row names the NSF/ANSI standard the category is tested under. A standard describes what the test covers. It does not mean every unit on the market carries that certification, so check the specific model against its listing before you buy.
| Contaminant | Standard | Note |
|---|---|---|
| Hardness, calcium and magnesium | NSF/ANSI 44 | |
| Barium and radium 226/228 | NSF/ANSI 44 | On models certified for those specific reductions. |
What it does not do
Every filter has a boundary. These are the things this one will not fix, listed so you can rule it out quickly if your problem is on the list.
- Chlorine taste and odour. Add carbon for that.
- Lead, PFAS, nitrates, or bacteria.
- Iron above the level the resin can handle, which fouls the bed instead.
When it fits
- Measured hardness is high enough to scale a water heater and shorten its life
- Scale is already visible on fixtures and inside kettles
- You are replacing appliances more often than you expect to
When it does not fit
- Hardness is mild and the only complaint is spotting on glassware
- You are on a sodium-restricted diet and cannot use a potassium alternative
- Local rules restrict brine discharge to the sewer, which some municipalities do
Space, services, and upkeep
A softener tank and a brine tank, roughly 3 feet by 2 feet of floor area, near a drain.
A drain connection is required. It needs a power outlet within reach. This is not a rental option, because it fixes to the building and stays there.
Replacement interval. Salt topped up every 4 to 8 weeks depending on household size and hardness. Resin bed typically lasts 10 to 15 years.
Problems this is used for
We recommend this equipment against these confirmed problems. Each page explains how to confirm the problem before spending anything, and when treatment is not warranted.
- Hard water. Dissolved calcium and magnesium picked up from limestone and other rock.
Property types where this comes up
Common questions
Does softened water taste salty?
No. Ion exchange releases sodium ions, not sodium chloride, and the quantity is proportional to how hard your water was. Very hard water produces a higher sodium content than mildly hard water. Most people notice no taste difference at all. If you are on a medically restricted sodium intake it is worth raising with a clinician, and potassium chloride can be used in place of salt at a higher running cost.
How much salt should it use?
It depends on your hardness and water use, but a typical household uses somewhere between one and two 40 pound bags a month. A sudden jump usually means the control valve is regenerating too often or a setting has drifted, and a sudden drop can mean it has stopped regenerating at all. Either is worth a call, because both waste money in different directions.
Can a softener remove iron?
A small amount, yes, and many units are rated for a limited iron load. Past that the iron coats the resin beads and stops them exchanging, which quietly kills the softener's capacity while it appears to run normally. Where a test shows meaningful iron we fit dedicated iron treatment ahead of the softener so the resin is protected.
Other filter types to compare
If the notes above rule this out, these are the neighbouring options worth reading before you decide.
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